Interventional radiology is a subspecialty of radiology in which minimally invasive procedures are performed using image guidance. Some of these procedures are done for purely diagnostic purposes (e.g., biopsy), while others are done for treatment purposes (e.g., radio frequency ablation). Pictures (images) are used to direct these procedures, which are usually done with needles or small catheters that are inserted into the body through the skin or through a body cavity or anatomical opening. The images allow the interventional radiologist to guide these instruments through the body to the areas of interest.
Common interventional imaging methods include X-ray fluoroscopy, computed tomography (CT), ultrasound (US), and magnetic resonance imaging (MRI).
When starting an interventional procedure the needle is introduced a little into the patient from a selected entry point. To verify the correct position and direction a set of control images are taken. Due to the weight of the needle, especially the weight of the portion of the needle which is outside the body, gravity will deflect the needle from its intended path. This makes it difficult to ensure that the needle hits the intended target, which can be a small area in the body.
The conventional approach is to advance towards the target by repeatedly adjusting the angle and inserting the needle little by little while constantly taking repeat images to verify position and direction. Every time an image is acquired any deflection of the needle would make an assessment of the correct direction more difficult. As the depth of the needle increases more tissue is there to support the needle. However, a heavy needle and/or a long needle would still suffer a deflection due to gravity and superficial lesions would not have enough tissue to stabilize a needle.
It is known to use a needle holder to guide and stabilize the needle at a chosen angle during image acquisition. When using a needle holder the user will get a firm idea of the planned direction of the needle and can use this information to redirect the needle until the correct angle is obtained. Once the desired angle is obtained the needle holder can help to steer the needle in the chosen direction, and when the needle is at the correct position the needle holder can be used to fix the needle at a chosen depth (when using a coaxial approach). Longer needles and/or heavier needles would typically need more support than short and light weighted ones.
Examples of known needle holders can be found in U.S. Pat. No. 4,883,053, U.S. Pat. No. 5,201,742 and WO 2004/021898. These documents disclose the use of a plate or base which is placed onto the patient and supports two guide members that intersect at an angle. The guide members are typically semi-circular or segments of a circle which are connected at their ends over two diameters of a circular base, where the diameters intersect at right angles. One or both of the guide members is connected to the base with hinges that enable rotation of the guide member to different angles. A clip or a tube for holding the needle is joined to the guide members in such a way that the needle can be pointed at any angle relative to the plane of the base. This is achieved by allowing the clip or tube to slide relative to one or both of the guide members, and by changing the angle of the guide members. A screw fitting can be used to tighten the connection between the clip or tube and the guide members, and/or between two guide members in order to fix the needle in place.
It is also known in alternative embodiments in some of the above references to use a spherical or part-spherical member which is moveably mounted to a part-spherical bearing surface to enable a needle passing through the spherical or part-spherical member to be pointed at a desired angle.
However, whilst these prior art devices can provide the necessary stability and guidance for a needle in an interventional radiology procedure, they restrict the actions of the radiologist in subsequent or preceding handling of the needle.